Saturday, October 13, 2012
Near Earth Object 2012 TC4 Flys by (12 October 2012)
Images taken form 2:00 UT on, when the 22 meter asteroid was just 5 hours from closest approach of a mere 0.2 Earth Moon distances away. Not satellite scraping, but still reasonably close.
ImageJ (click to embiggen for full asteroidal awesomeness). Images were processed with fairly strong adjustment to brightness and contrast.
There is a very large difference in the brightness of the asteroid in these images (look carefully for the first one, it zips through the bright star image). This implies the asteroid is rapidly rotating and of uneven shape or colour.
After catching 2012 TC4 in iTelescope T14 yesterday, I was all fired up to get it as it was near closest approach.
Under these circumstances trying to track the asteroid with one-line elements would fail (the scopes drives can't push it that fast).
So I used my standard technique, which is to choose a star not far from where the asteroid would be, and set that as the target, then wait for the asteroid to zoom by. "Would be" was the operative word. The asteroid was moving so fast that by the time the telescope slewed to the position were the asteroid was, it would have moved out of frame.
So I measured the time T5 took to slew, autofocus and begin imaging in a series of recent images, and used the average time from start of my run to actual imaging (around 5 minutes) to set the telescope position.
I started the run exactly at astronomical twilight (1:55 UT), and set up the image area to cover where the asteroid would be 5 minutes later. And lo and behold it worked!
My previous shots of 2012 TC4 are here.
closest approach was planned on
2:00 UT or 5 hours from closest approach ?